High performance liquid chromatography (or high pressure liquid chromatography, HPLC) and ultra high performance liquid chromatography (UHPLC) are both a form of column chromatography used frequently in biochemistry and analytical chemistry to separate, identify, and quantify compounds. HPLC and UHPLC utilize an HPLC column that holds chromatographic packing material (stationary phase), a pump that moves the mobile phase(s) through the HPLC column, and a detector that shows the retention times of the molecules. Retention time varies depending on the interactions between the stationary phase, the molecules being analyzed, and the solvent(s) used. In HPLC analysis, the sample is pumped through the HPLC column under an elevated pressure, typically at 300 to 6,000 psi, and in UHPLC, analysis, system pressure extends upward to 1400 bar or 20,000 psi or higher.
Liquid chromatography-mass spectrometry (LC/MS) is an analytical chemistry technique that combines the physical separation capabilities of liquid chromatography with the mass analysis capabilities of mass spectrometry. LC/MS is a powerful technique used for many applications which has very high sensitivity and specificity. Generally its application is oriented towards the specific detection and potential identification of chemicals in the presence of other chemicals (in a complex mixture).
Often a sample bound for HPLC, UHPLC, or LC/MS analysis requires some type of clean-up to ensure optimal results. Detergents or salts can affect the ionization process, while overly dilute samples can be swamped out by background noise, making them undetectable. Trap columns are small packed beds that use the adsorptive properties of analytes to effectively concentrate dilute samples, desalt, remove detergents, and more. Trap columns have the advantage of being able to be used in a completely on-line environment. The trap column is normally of a certain design and material specifically suited for a certain compound or class of compounds. For instance, Optimize Technologies offers two lines of trap columns to suit trapping needs. The OPTI-PAK® capillary traps are designed for ultra-low volume applications where any excess in volume could be detrimental to the assay. OPTI-LYNX™ traps offer higher capacity. Both formats are available in a number of different phases and support materials such that a user may choose the trap design and material that best fits the situation.
All of the various components and lengths of tubing used in HPLC, UHPLC, and LC/MS analysis are typically interconnected by fitting assemblies, such as those described in prior patents and pending applications, for example, U.S. Pat. Nos. 5,525,303; 5,669,637; 5,730,943; 5,911,954; 6,000,916; and 6,095,572, and U.S. patent application Ser. No. 11/971,834, filed on Jan. 9, 2008, the disclosures of which are herein all incorporated by reference herein. For instance, the fitting assemblies may include a first and second fitting subassembly that receives an insert therebetween, such as a column, to place the column into fluid communication with the tubing. It is advantageous if the fitting assembly provides a true zero-dead-volume connection between the analytical components to minimize dead space in the flow path. Moreover, it is beneficial to minimize the tubing length required to couple the column to the analytical instrument. Adding tubing length to the connection significantly degrades the analysis, for example, by adding band broadening.
Moreover, during HPLC, UHPLC, and LC/MS analysis, it is desirable to be able to quickly change the HPLC columns, the trap columns, or other columns being used when, for example, the column needs to be removed for maintenance or reconfiguration. Moreover, the column often needs to be replaced with a different column having a certain design, dimension, or packing material specifically suited for a certain compound or class of compounds. Columns must also be replaced when they become saturated or contaminated.
Changing the column requires the operator to manually disconnect the fitting assembly and replace the column. This time-consuming process decreases throughput and efficiency. This is especially true when the sample being analyzed is a dangerous substance that requires the use of a glove box or another suitable enclosed area. Thus, it is desired to provide an efficient, automated process and apparatus for changing/replacing columns in an HPLC, UHPLC, LC/MS, or a similar analytical system with minimal disruption. Moreover, it is desirable that the apparatus be suitable for a small space so that the apparatus may be placed in a location that minimizes the length of tubing needed in the system.